Pilot pattern design for an OFDM system

ABSTRACT

The present invention relates to a transmitting device and a receiving device in a wireless orthogonal frequency division multiplex (OFDM) communication system with space time transmit diversity (STTD). Further, the present invention relates to a channel estimation method for performing a channel estimation in such a wireless communication system, in which the transmitting device comprises a first and a second antenna for transmitting signals with space time transmit diversity. The first and the second antenna means are arranged spaced apart from each other in a space diversity arrangement, whereby first and second pilot symbols are transmitted via said first and said second antenna means, respectively. Some of the second pilot symbols are orthogonal to corresponding ones of the first pilot symbols, so that a channel estimation to separately determine the transmission quality of signals transmitted from the first and the second antenna means, respectively, can be performed in a receiving device which receives the signals with only one single antenna.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.09/898,389, filed Jul. 3, 2001, now U.S. Pat. No. 7,221,645 B1, andclaims the benefit of the priority from European Patent Application No.00114423.7, filed Jul. 5, 2000, the entire contents of each of which areincorporated herein by reference.

The present invention relates to a transmitting device of a wirelessorthogonal frequency division multiplex (OFDM) communication system.

In wireless telecommunication, the transmission quality between atransmitting device, such as a base station, and a receiving device,such as a mobile terminal, depends strongly on the respectivetransmission environment and is often deteriorated by fading effects andthe like. This often leads to poor speech and data transmission quality,particularly if only one single antenna is used on the transmission sideand one single antenna is used on the receiving side. Therefore, somemobile terminals for wireless telecommunication systems, such as the GSMsystem, comprise two or more and different kinds of antennas built asinternal or external antennas in the mobile terminal. However, it isdesirable that modern mobile terminals are as small and light aspossible and therefore it is an increasing interest to use only a singleantenna in these mobile terminals. In order to allow the use of only asingle antenna on the receiving side, particularly the mobile terminalside, it has been proposed to use more than one antenna on thetransmitting side, particularly the base station side, so that thediversity gain can be used for a better transmission quality. Thisscheme is called transmit diversity. Transmit diversity generally meansthat more than one antenna, e.g. two antennas, transmit datasimultaneously to a receiving device. If the same data are transmittedin parallel by two antennas, the receiving side has a chance to receivesignals at least from one of the antennas with an acceptabletransmission quality so that a good connection can be ensured. Onespecific approach in the transmit diversity scheme is the use of aso-called space time coding. The resulting space time transmit diversity(STTD) has been adapted and is part of the UMTS standard for the nextgeneration of mobile telecommunication.

In a space time transmit diversity system, a transmitting device, suchas a base station, comprises e.g. two antennas arranged spaced apartfrom each other in a space diversity arrangement. A stream of data to betransmitted to a receiving device, such as a mobile terminal, is encodedand processed so that two parallel data streams are generated. Afterfurther processing corresponding to the respective wirelesscommunication system, the data of each of the two data streams aretransmitted by a respective one of the two antennas. Although generallythe same data content is transmitted by each of the two antennas, thesignals transmitted by the two antennas are not absolutely identical,but data symbols to be transmitted are mapped or coded slightlydifferently on the signals transmitted by each of the antennas. Thisallows a receiving device receiving the signals transmitted from the twoantennas with only a single antenna to distinguish and separate signalscoming from one of the transmitting antennas from signals coming fromthe other of the transmitting antennas. Since the two transmittingantennas are arranged in a space diversity arrangement, crossinterference is avoided and the receiving device can then, after acorresponding channel estimation, distinguish and combine the signalsfrom the two transmitting antennas to obtain a better transmissionquality. The channel estimation in the receiving device is usuallyperformed on the basis of pilot symbols transmitted from thetransmitting device. The receiving device performs a channel estimationby comparing received pilot symbols with an expected pilot symbol tomeasure the channel response and to tune the receiving device to thebest transmission channel, i.e. the transmitting antenna to which thebetter connection exists.

The above-mentioned UMTS system bases on a code division multiple access(CDMA) scheme. The CDMA scheme is only one of several possible multipleaccess schemes used in wireless telecommunication. For wirelesstelecommunication with high data rates, the orthogonal frequencydivision multiplex (OFDM) scheme is known, in which the availablefrequency band used for a communication is divided in a plurality offrequency subcarriers, whereby adjacent frequency subcarriers arerespectively orthogonal to each other.

The object of the present invention is now to propose a transmittingdevice for a wireless OFDM communication system, which allows a simpleand effective channel estimation to be performed.

This object is achieved by a transmitting device according to theindependent claims.

According to one aspect, the present invention relates to a transmittingdevice for transmitting data symbols and pilot symbols in an OFDMtransmission system having a plurality of transmission antennas; thedevice comprising symbol generating means for generating said datasymbols and said pilot symbols, means for transmitting said data symbolsand pilot symbols respectively by using a plurality of subcarriers ofsaid OFDM transmission system via said plurality of transmissionantennas, wherein said symbol generating means generates a first typepilot symbol and a second type pilot symbol having an inverted value ofsaid first type pilot symbol so that a pilot symbol pattern in thefrequency dimension contains at least said first type pilot symbol to betransmitted by using a predefined subcarrier and second type pilotsymbol to be transmitted by using another predefined subcarrier, andwherein said pilot symbol pattern to be transmitted by using one of saidplurality of transmission antennas has a different pattern from a pilotsymbol pattern to be transmitted by using another transmission antenna.

According to a further aspect, the present invention relates to atransmitting device for transmitting data symbols and pilot symbols inan OFDM transmission system having a plurality of transmission antennas;the device comprising symbol generating means for generating said datasymbols and said pilot symbols, means for transmitting said data symbolsand pilot symbols by using a plurality of subcarriers of said OFDMtransmission system via said plurality of transmission antennas, whereinsaid symbol generating means generates a first type pilot symbol and asecond type pilot symbol having an inverted value of said first typepilot symbol so as to create a pilot symbol pattern in where said firstand second type pilot symbols are allocated respectively in saidfrequency dimension, and wherein said pilot symbol pattern to betransmitted by using one of said plurality of transmission antennas hasa different pattern from a pilot symbol pattern to be transmitted byusing another transmission antenna.

According to a further aspect, the present invention relates to atransmitting device for transmitting data symbols and pilot symbols inan OFDM transmission system; the device comprising symbol generatingmeans for generating said data symbols and said pilot symbols, means fortransmitting said data symbols and pilot symbols by using a plurality ofsubcarriers of said OFDM transmission system via a plurality oftransmission antennas, wherein said symbol generating means assignseither a first type pilot symbol or a second type pilot symbol having aninverted value of said first type pilot symbol to said generated pilotsymbols in the frequency dimension so that a pilot symbol patterncomprising said first and second type pilot symbols to be transmitted byusing one of said plurality of transmission antennas has a differentpattern from a pilot symbol pattern to be transmitted by using anothertransmission antenna.

According to a further aspect, the present invention relates to atransmitting device for transmitting data symbols and pilot symbols inan OFDM transmission system; the device comprising symbol generatingmeans for generating said data symbols and said pilot symbols, means fortransmitting said data symbols and pilot symbols by using a plurality ofsubcarriers of said OFDM transmission system via a plurality oftransmission antennas, wherein said symbol generating means is designedto create a pilot symbol pattern in the frequency direction comprisingat least a first type pilot symbol and a second type pilot symbol havingan inverted value of said first type pilot symbol, wherein said pilotsymbol pattern assigned to one of said plurality of transmissionantennas has a different pattern from a pilot symbol pattern assigned toanother transmission antenna.

According to a further aspect, the present invention relates totransmitting device for transmitting data symbols and pilot symbols inan OFDM transmission system having a plurality of transmission antennas;the device comprising symbol generating means for generating said datasymbols and said pilot symbols, means for transmitting said data symbolsand pilot symbols respectively by using a plurality of subcarriers ofsaid OFDM transmission system via said plurality of transmissionantennas, wherein said symbol generating means generates a first typepilot symbol and a second type pilot symbol having an inverted value ofsaid first type pilot symbol so that a pilot symbol pattern in the timedimension comprises at least said first and second type pilot symbols tobe transmitted at different timepoints respectively, and wherein saidpilot symbol pattern to be transmitted by using one of said plurality oftransmission antennas is different from a pilot symbol pattern to betransmitted by using another transmission antenna.

According to a further aspect, the present invention relates to atransmitting device for transmitting data symbols and pilot symbols inan OFDM transmission system having a plurality of transmission antennas;the device comprising symbol generating means for generating said datasymbols and said pilot symbols, means for transmitting said data symbolsand pilot symbols by using a plurality of subcarriers of said OFDMtransmission system via said plurality of transmission antennas, whereinsaid symbol generating means generates a first type pilot symbol and asecond type pilot symbol having an inverted value of said first typepilot symbol so as to create a pilot symbol pattern in where said firstand second type pilot symbols are regularly allocated in the timedimension, and wherein said pilot symbol pattern to be transmitted byusing one of said plurality of transmission antennas is different from apilot symbol pattern to be transmitted by using another transmissionantenna.

According to a further aspect, the present invention relates to atransmitting device for transmitting data symbols and pilot symbols inan OFDM transmission system; the device comprising

symbol generating means for generating said data symbols and said pilotsymbols,

means for transmitting said data symbols and pilot symbols by using aplurality of subcarriers of said OFDM transmission system via aplurality of transmission antennas,

wherein said symbol generating means assigns either a first type pilotsymbol or a second type pilot symbol having an inverted value of saidfirst type pilot symbol to said generated pilot symbols in the timedimension so that a pilot symbol pattern comprising said first andsecond type pilot symbols to be transmitted by using one of saidplurality of transmission antennas is a different pattern from a pilotsymbol pattern to be transmitted by using another transmission antenna.

According to a further aspect, the present invention relates to atransmitting device for transmitting data symbols and pilot symbols inan OFDM transmission system; the device comprising symbol generatingmeans for generating said data symbols and said pilot symbols, means fortransmitting said data symbols and pilot symbols by using a plurality ofsubcarriers of said OFDM transmission system via a plurality oftransmission antennas, wherein said symbol generating means is designedto generate either a first type pilot symbol and a second type pilotsymbol having an inverted value of said first type pilot symbol in thetime dimension as a type of said generated pilot symbols, wherein saidpilot symbol pattern, comprising said first and second type pilotsymbols allocated in the time direction, which is assigned to one ofsaid plurality of transmission antennas is a different pattern from apilot symbol pattern which is assigned to another transmission antenna.

According to a further aspect, the present invention relates to a Atransmitting device for transmitting data symbols and pilot symbols inan OFDM transmission system having a plurality of transmission antennas;the device comprising symbol generating means for generating said datasymbols and said pilot symbols, means for transmitting said data symbolsand pilot symbols respectively by using a plurality of subcarriers ofsaid OFDM transmission system via said plurality of transmissionantennas, wherein said symbol generating means generates a first typepilot symbol and a second type pilot symbol being orthogonal to saidfirst type pilot symbol so that a pilot symbol pattern in the frequencydimension contains at least said first type pilot symbol to betransmitted by using a predefined subcarrier and second type pilotsymbol to be transmitted by using other predefined subcarrier, andwherein said pilot symbol pattern to be transmitted by using one of saidplurality of transmission antennas has a different pattern from a pilotsymbol pattern to be transmitted by using another transmission antenna.

According to a further aspect, the present invention relates to atransmitting device for transmitting data symbols and pilot symbols inan OFDM transmission system having a plurality of transmission antennas;the device comprising symbol generating means for generating said datasymbols and said pilot symbols, means for transmitting said data symbolsand pilot symbols by using a plurality of subcarriers of said OFDMtransmission system via said plurality of transmission antennas, whereinsaid symbol generating means generates a first type pilot symbol and asecond type pilot symbol being orthogonal to said first type pilotsymbol so as to create a pilot symbol pattern in where said first andsecond type pilot symbols are allocated respectively in said frequencydimension, and wherein said pilot symbol pattern to be transmitted byusing one of said plurality of transmission antennas has a differentpattern from a pilot symbol pattern to be transmitted by using anothertransmission antenna.

According to a further aspect, the present invention relates to atransmitting device for transmitting data symbols and pilot symbols inan OFDM transmission system; the device comprising symbol generatingmeans for generating said data symbols and said pilot symbols, means fortransmitting said data symbols and pilot symbols by using a plurality ofsubcarriers of said OFDM transmission system via a plurality oftransmission antennas, wherein said symbol generating means assignseither a first type pilot symbol or a second type pilot symbol beingorthogonal to said first type pilot symbol to said generated pilotsymbols in the frequency dimension so that a pilot symbol patterncomprising said first and second type pilot symbols to be transmitted byusing one of said plurality of transmission antennas has a differentpattern from a pilot symbol pattern to be transmitted by using anothertransmission antenna.

According to a further aspect, the present invention relates to a Atransmitting device for transmitting data symbols and pilot symbols inan OFDM transmission system; the device comprising symbol generatingmeans for generating said data symbols and said pilot symbols, means fortransmitting said data symbols and pilot symbols by using a plurality ofsubcarriers of said OFDM transmission system via a plurality oftransmission antennas, wherein said symbol generating means is designedto create a pilot symbol pattern in the frequency direction comprisingat least a first type pilot symbol and a second type pilot symbol beingorthogonal to said first type pilot symbol, wherein said pilot symbolpattern assigned to one of said plurality of transmission antennas has adifferent pattern from a pilot symbol pattern assigned to anothertransmission antenna.

According to a further aspect, the present invention relates to a Atransmitting device for transmitting data symbols and pilot symbols inan OFDM transmission system having a plurality of transmission antennas;the device comprising symbol generating means for generating said datasymbols and said pilot symbols, means for transmitting said data symbolsand pilot symbols respectively by using a plurality of subcarriers ofsaid OFDM transmission system via said plurality of transmissionantennas, wherein said symbol generating means generates a first typepilot symbol and a second type pilot symbol being orthogonal to saidfirst type pilot symbol so that a pilot symbol pattern in the timedimension comprises at least said first and second type pilot symbols tobe transmitted at different timepoints respectively, and wherein saidpilot symbol pattern to be transmitted by using one of said plurality oftransmission antennas is different from a pilot symbol pattern to betransmitted by using another transmission antenna.

According to a further aspect, the present invention relates to a Atransmitting device for transmitting data symbols and pilot symbols inan OFDM transmission system having a plurality of transmission antennas;the device comprising symbol generating means for generating said datasymbols and said pilot symbols, means for transmitting said data symbolsand pilot symbols by using a plurality of subcarriers of said OFDMtransmission system via said plurality of transmission antennas, whereinsaid symbol generating means generates a first type pilot symbol and asecond type pilot symbol being orthogonal to said first type pilotsymbol so as to create a pilot symbol pattern in where said first andsecond type pilot symbols are regularly allocated in the time dimension,and wherein said pilot symbol pattern to be transmitted by using one ofsaid plurality of transmission antennas is different from a pilot symbolpattern to be transmitted by using another transmission antenna.

According to a further aspect, the present invention relates to a Atransmitting device for transmitting data symbols and pilot symbols inan OFDM transmission system; the device comprising symbol generatingmeans for generating said data symbols and said pilot symbols, means fortransmitting said data symbols and pilot symbols by using a plurality ofsubcarriers of said OFDM transmission system via a plurality oftransmission antennas, wherein said symbol generating means assignseither a first type pilot symbol or a second type pilot symbol beingorthogonal to said first type pilot symbol to said generated pilotsymbols in the time dimension so that a pilot symbol pattern comprisingsaid first and second type pilot symbols to be transmitted by using oneof said plurality of transmission antennas is a different pattern from apilot symbol pattern to be transmitted by using another transmissionantenna.

According to a further aspect, the present invention relates to a Atransmitting device for transmitting data symbols and pilot symbols inan OFDM transmission system; the device comprising symbol generatingmeans for generating said data symbols and said pilot symbols, means fortransmitting said data symbols and pilot symbols by using a plurality ofsubcarriers of said OFDM transmission system via a plurality oftransmission antennas, wherein said symbol generating means is designedto generate either a first type pilot symbol and a second type pilotsymbol being orthogonal to said first type pilot symbol in the timedimension as a type of said generated pilot symbols, wherein said pilotsymbol pattern, comprising said first and second type pilot symbolsallocated in the time direction, which is assigned to one of saidplurality of transmission antennas is a different pattern from a pilotsymbol pattern which is assigned to another transmission antenna.

The proposed scheme of transmitting, receiving and processing first andsecond pilot symbols allows a simple and effective channel estimationprocessing to be performed on the receiving side so that a bettercoherent demodulation of the transmission channel can be performed toensure the best transmission quality. In an advantageous aspect, thepresent invention ensures full space and time diversity. Further, nofeedback information from the receiving side to the transmitting side isrequired and an improved data transmission capacity can be realised.Further, the proposed system is robust to transmission antenna failuresand guarantees power amplifier balance on the transmitting side.

Advantageously, the corresponding first and second pilot symbolstransmitted from the first and the second antenna means of thetransmitting device, respectively, have the same frequency and timeallocation in the OFDM system. In other words, corresponding first andsecond pilot symbols are transmitted in the same subcarrier and in thesame time slot of the OFDM system. Hereby, the first and the secondpilot symbols advantageously are alternatingly identical and orthogonalto each other in the frequency as well as in the time dimension. Thismeans that in the frequency and time grid of the OFDM system, identicalfirst and second pilot symbols and orthogonal first and second pilotsymbols alternate with each other in the frequency as well as in thetime dimension.

It has to be clarified at this point that the single antenna of areceiving device receives the first pilot symbols transmitted from thefirst antenna means and the second pilot symbols transmitted from thesecond antenna means of the transmitting device only as a combined orsuperimposed pilot symbol. In case that the first pilot symbol and thesecond pilot symbol transmitted in the same frequency subcarrier and thesame timepoint are identical, the receiving device receives a combinedpilot symbol comprising the superimposed identical first and secondpilot symbol. In case that the first and second pilot symbol areorthogonal to each other, the receiving device receives a combined pilotsymbol comprising the superimposed orthogonal first and second pilotsymbol. In the receiving device, the transfer function of the first andthe second pilot symbol, respectively, can therefore be separated sothat the respective channel estimation for each of the two transmissionantennas can be performed in a simple way.

Advantageously, the second pilot symbols alternatingly have theidentical and the inverse complex value of the corresponding first pilotsymbol in the time as well as in the frequency dimension, so that theprocessing and the channel estimation on the receiving side can beperformed on a basis of a simple addition and subtraction calculation ofthe received pilot symbols. On the basis of the channel estimationresult, both signals from the first antenna means and from the secondantenna means of the transmitting device are further processed and usedas the communication data in the receiving device.

The transmitting device according to the present invention can e.g. beimplemented in the base station of a OFDM communication system and thereceiving device according to the present invention can e.g. beimplemented in a mobile terminal of a OFDM communication system.

In the following description, the present invention is explained in moredetail in relation to the enclosed drawings, in which

FIG. 1 shows schematically a base station comprising a transmittingdevice according to the present invention,

FIG. 2 shows schematically a mobile terminal comprising a receivingdevice according to the present invention,

FIGS. 3A and 3B a first and a second example, respectively, of a pilotsymbol pattern transmitted by a first antenna means of a transmittingdevice according to the present invention, and

FIGS. 4A and 4B a first and a second example, respectively, of a pilotsymbol pattern transmitted by the second antenna means of thetransmitting device according to the present invention.

In FIG. 1, the block diagram of a base station 1 of a wirelessorthogonal frequency division multiplex (OFDM) communication system is,shown, which comprises a transmitting device according to the presentinvention. It is to be understood that in FIG. 1 only elements importantfor the understanding of the present invention are shown. Furtherelements, such as coding means, modulation means, RF part and the likenecessary for the operation of the base station are omitted for the sakeof clarity.

The base station 1 comprises a first antenna 5 and a second antenna 6being arranged spaced apart from each other, e. g. in a space diversityarrangement. In thus case, the first antenna 5 may also be called anon-diversity antenna and the second antenna 6 can also be called adiversity antenna. The space diversity arrangement of the first antenna5 and the second antenna 6 is so that the two antennas 5 and 6 aresufficiently separated in space, so that the signals transmitted by thefirst antenna 5 and the second antenna 6, respectively, are uncorrelatedand an effective diversity gain can be achieved on the receiving side.

Further, the base station 1 comprises a encoding means 3 for encoding adata stream, e. g. on the basis of a space time transmit diversity(STTD) scheme and outputting a first and a second STTD encoded datastream to a multiplexer 4. The first STTD encoded data stream is to betransmitted via the first antenna 5 and the second STTD encoded datastream is to be transmitted via the second antenna 6. Although the datatransmitted from the first antenna 5 and the second antenna 6 aregenerally the same data, i.e. contain the data of the single data streamsupplied to the encoding means 3, the data are not transmittedidentically by the two antennas 5 and 6. For example, the datatransmitted by the first antenna 5 identically correspond to the dataarrangement of the single data stream supplied to the encoding means 3.If, e.g. a first data symbol S₁ in a time period 0-T and a second datasymbol S₂ in the succeeding time period T-2T are supplied to theencoding means 3, the first data stream output by the encoding means canidentically correspond to that arrangement (data symbol S₁ followed bydata symbol S₂). The second data stream output by the encoding means 3,however, contains the data symbols S₁ and S₂ in a different arrangement.For example, as shown in FIG. 1, in the second data stream, the datasymbol of the first time period 0-T could be the negative complexconjugated value of the second data block S₂ of the first data stream,i.e. −S*₂. The next succeeding data symbol of the second data stream isthe conjugated complex value of the first data symbol S₁ of the firstdata stream, i.e. S*₁. Thus, the second data stream contains theidentical data content as the first data stream, but in a differentarrangement. A receiving device receiving the signals from the firstantenna 5 and the second antenna 6 as superimposed signals is thereforeable to clearly distinguish between the signals transmitted from thefirst antenna 5 and the signals transmitted from the second antenna 6due to the space diversity arrangement and the different arrangement ofthe same data content. It is to be understood that the space timetransmit diversity scheme shown in and explained in relation to FIG. 1only serves as an example to explain the present invention. Any otherSTTD scheme for transmitting data via the first antenna 5 and the secondantenna 6 can be applied.

The base station 1 further comprises a pilot symbol generating means 2for generating pilot symbols to be transmitted among the data of thefirst and the second data stream by the first antenna 5 and the secondantenna 6. Thereby, the pilot symbol generating means 2 generates andsupplies different pilot symbol patterns to be transmitted via the firstantenna 5 and the second antenna 6, respectively, to the multiplexer 4.The general idea of the present invention is that some of the pilotsymbols transmitted by the first antenna 5 and the second antenna 6 areorthogonal to each other so that the cross-interference from bothantennas 5 and 6 is eliminated, the signals from the first,(non-diversity) antenna 5 and the second (diversity) antenna 6 can bedifferentiated and consequently a separate channel estimation for eachantenna 5, 6 can be achieved in a receiving device.

FIG. 2 shows a schematic block diagram of a mobile terminal 10comprising a receiving device for receiving signals in a wireless OFDMcommunication system according to the present invention. Particularly,the mobile terminal 10 is adapted to receive signals from a base station1 as shown in FIG. 1.

The mobile terminal 10 comprises a single antenna 11 for receiving STTDencoded signals as well as pilot symbols transmitted from the firstantenna 5 and the second antenna 6 of the base station 1. Further, themobile terminal 10 comprises a receiving means 12, which comprises e.g.the necessary RF part and the like. Further, the mobile terminal 10comprises a demodulation means for demodulating signals received by thereceiving means 12 via the antenna 11. It is to be understood that themobile terminal 10 further comprises all necessary elements to beoperated in the corresponding wireless OFDM system. However, theseelements are not shown for the sake of clarity.

The mobile terminal 10 further comprises a processing means 14 fordetecting pilot symbols in the signals received by the receiving means12 via the antenna 11. The processing means 14 processes detected pilotsymbols and performs a channel estimation on the basis of the processingto separately determine the transmission quality of the received signalstransmitted from the first antenna 5 and the second antenna 6,respectively. In other words, by processing the received pilot symbols,which are combined pilot symbols comprising the first and the secondpilot symbols simultaneously transmitted by the first antenna 5 and thesecond antenna 6, the processing means 14 is able to separatelydetermine the transmission quality of the signals transmitted from thefirst antenna 5 and the transmission quality of the signals transmittedfrom the second antenna 6. On the basis of this channel estimationresult, both the STTD encoded signals from the first antenna 5 and fromthe second antenna 6 are further processed and used as communicationdata in the mobile terminal 10.

As stated above, at least some of the second pilot symbols transmittedfrom the second antenna 6 are orthogonal to corresponding first pilotsymbols transmitted by the antenna 5. The processing performed in theprocessing means 14 bases on this orthogonality of the first and thesecond pilot symbols and enables the separate channel estimation for thefirst and the second antenna 5 and 6, respectively. In relation to FIGS.3 and 4, a specific example for pilot symbol patterns to be transmittedby the base station 1 and to be received and processed in the mobileterminal 10 are proposed.

FIG. 3 comprises two FIGS. 3A and 3B. FIG. 3A shows a first example of apilot symbol pattern to be transmitted by the first (non-diversity)antenna 5 of the base station 1. The shown pilot symbol pattern has aregular distribution in the time and the frequency dimension of the OFDMsystem. The pilot symbols 20, 21, . . . , 28 are always transmitted inthe same frequency subcarriers and in equidistant timepoints. Forexample, the pilot symbols 20, 21 and 22 are transmitted in a firstfrequency subcarrier, whereby respectively four data symbols aretransmitted between adjacent pilot symbols 20, 21 and 21, 22. Pilotpatterns 23, 24 and 25 are transmitted in a second frequency subcarrierand the pilot symbol 26, 27 and 28 are transmitted in a third frequencysubcarrier. Thereby, the pilot symbols 20, 23 and 26 are transmitted atthe same first timepoint, the pilot symbols 21, 24 and 27 aretransmitted in the same second timepoint and the pilot symbols 22, 25and 28 are transmitted in the same third timepoint. Thus, always thesame frequency subcarriers are used for the transmission of the pilotsymbols and the transmission of the pilot symbols in the respectivesubcarriers always takes place at equidistant timepoints. Such a pilotsymbol pattern is known from prior art OFDM systems. On the receivingside, the channel estimation for the data symbols between adjacent pilotsymbols (in frequency and time) is performed by e.g. linearinterpolation. For example, for the data symbols between the pilotsymbols 20 and 21 in the same frequency subcarrier, a linearinterpolation of the pilot symbols 20 and 21 is performed on thereceiving side. For the data symbols between the adjacent pilot symbols20 and 23 received at the same timepoint but in different frequencysubcarriers, a linear interpolation is also performed. For data symbolsin frequency subcarriers, in which no pilot symbols are transmitted, acombination of a time and a frequency interpolation of the respectiveadjacent pilot symbols is performed.

FIG. 3B shows also a regular distribution of the first pilot symbols tobe transmitted by the first antenna 5 of the base station 1. Thedifference to the pilot symbol pattern of FIG. 3A is here that the (intime) succeeding pilot symbols are not transmitted in the same frequencysubcarrier as the preceding pilot symbol, but in the immediatelyadjacent subcarrier. For example, the pilot symbol 31 is not transmittedin the same frequency subcarrier as the preceding pilot symbol 30, butthe immediately adjacent (lower) frequency subcarrier. This pilot symbolpattern may allow a more accurate channel estimation for data symbols offrequency subcarriers, in which no pilot symbols are transmitted.Identical to the pilot symbol pattern proposed in FIG. 3A, the pilotsymbols of the pilot symbol pattern proposed in FIG. 3B are alsotransmitted at identical timepoints. Thus, pilot symbols 30, 34 and 38are transmitted at the first identical timepoint, pilot symbols 31, 35and 39 are transmitted at the same second timepoint, pilot symbols 32,26 and 40 are transmitted at the same third timepoint and pilot symbols33, 37 and 41 are transmitted at the same fourth timepoint.

FIG. 4 comprises two FIGS. 4A and 4B, whereby FIG. 4A shows the pilotsymbol pattern for the second pilot symbols to be transmitted by thesecond antenna 6 of the base station 1, which corresponds to the pilotsymbol pattern of the first pilot symbols shown in FIG. 3A. As can beseen, also the pilot symbol pattern of FIG. 4A shows a very regulardistribution of pilot symbols 42, 43, . . . , 53 in frequency and time.The second pilot symbols are always transmitted in the same frequencysubcarrier and at the same timepoint as the corresponding first pilotsymbol. For example, the second pilot symbol 42 is transmitted in thesame frequency subcarrier and at the same timepoint as the correspondingfirst pilot symbol 20. The second pilot symbol 43 is transmitted in thesame frequency subcarrier and at the same timepoint as the first pilotsymbol 21. The second pilot symbol 46 corresponds to the first pilotsymbol 23, the second pilot symbol 50 corresponds to the first pilotsymbol 26 and so on. Thereby, the second pilot symbols of the pilotsymbol pattern in FIG. 4A are alternatingly identical and orthogonal tothe corresponding first pilot symbols of the pilot symbol pattern shownin FIG. 3A. The second pilot symbols 42, 44, 47, 50 and 52 are identicalto their corresponding first pilot symbols 20, 22, 24, 26 and 28.However, every other second pilot symbol (in time and frequencydimension) is the inverse complex value of the corresponding first pilotsymbol. For example, a second pilot symbol 43 is the inverse complexvalue of the first pilot symbol 21, the second pilot symbol 46 is theinverse complex value of the first pilot symbol 23. The same is true forthe second pilot symbol 48 and the first pilot symbol 25 and the secondpilot symbol 51 and the first pilot symbol 27. Thus, pairs of adjacentsecond pilot symbols, as e.g. the second pilot symbols 42 and 43 as wellas the second pilot symbols 42 and 46 are orthogonal to thecorresponding pairs of the first pilot symbols, e.g. first pilot symbol20 and 21 or first pilot symbol 20 and 23. Thus, orthogonality in thefrequency as well as in the time dimension is ensured.

The same is essentially true for the pilot symbol pattern shown in FIG.4B, which corresponds to the pilot symbol pattern shown in FIG. 3B.Similarly, the pilot symbols of the pilot symbol pattern shown in FIG.4B are alternatingly identical and orthogonal (inverse complex) to thecorresponding first pilot symbols shown in FIG. 3B.

The pilot symbol scheme proposed by the present invention can be appliedto any linear channel estimation algorithm in wireless OFDMcommunications. For the sake of clarity, a simple two pilot symbolaverage based channel estimation algorithm for the pilot symbol patternsof FIG. 3A and FIG. 4A is used as an example in the following furtherdetailed description.

Assuming that the complex values of all first pilot symbols 20, 21, . .. , 28 and the corresponding second pilot symbols having the identicalvalue, i.e. second pilot symbols 42, 44, 47, 50, 52, . . . , is A. Thecomplex value of the second pilot symbols 43, 46, 48, 51, . . . , havinga corresponding orthogonal value is then −A. For all the data symbolsbetween the succeeding pilot symbols 20 and 21 or 42 and 43, respectivechannel estimation values for the first (non-diversity) antenna 5 andthe second (diversity) antenna 6 should be obtained reliably so that theSTTD scheme can be applied.

As stated above, the antenna 11 and the receiving means 12 of the mobileterminal 10 receive the first and the second pilot symbols assuperimposed or combined pilot symbols. Thus, let y₁ and y₂ be thereceived values from the first 20, 21 and the second 42, 43 pilotsymbols. Since the time delay between the first and the second antenna5, 6 is negligible, the following equations are valid:y ₁ =A×h ₁ ¹ +A×h ₁ ² +n ₁andy ₂ =A×h ₂ ¹ −A×h ₂ ² +n ₂,whereby h₁ ¹ is the channel transfer function from the first antenna 5to the receiving antenna 11 for the first pilot symbol 20 with value“A”, h₁ ² is the channel transfer function from the second antenna 6 tothe receiving antenna 11 for the corresponding second pilot symbol 42with value “A”, h₂ ¹ is the channel transfer function from the firstantenna 5 to the receiving antenna 11 for the first pilot symbol 21 withvalue “A”, and h₂ ² is the channel transfer function from the secondantenna 6 to the receiving antenna 11 for the corresponding second pilotsymbol 43 with value “−A”. n₁ and n₂ are the noise values. If y₁+y₂ isused as the channel estimation for the first (non-diversity) antenna 5and y₁−y₂ is used as the channel estimation for the second (diversity)antenna 6, the signals from the first and the second antenna can bedifferentiated, the cross-interference can be eliminated and a reliablechannel estimation for both antennas 5 and 6 can be obtained in theprocessing means 14 of the mobile terminal 10, if the channel transferfunction is assumed to be kept fixed within the interval between thepreceding and the succeeding pilot symbols across the time dimension,i.e. h₁ ¹=h₂ ¹ and h₁ ²=h₂ ².

Thus, in the mobile terminal 10 the signals from the first and thesecond transmitting antenna 5, 6 can be differentiated and consequentlya separate channel estimation for each antenna 5, 6 can be achieved.Since the pilot patterns of the first and the second pilot symbols areorthogonal, the cross-interference from the first and the second antenna5 and 6, can be eliminated. Thus, a STTD scheme can be used in a highdata rate OFDM wireless communication system. It is to be noted, thatthe idea of the present invention can also be applied to OFDM basedbroadband radio access networks (BRAN), like HIPERLAN Type 2 systems. Inthis case, the pilot symbols are transmitted in preamble parts of arespective data burst comprising a preamble part and a data part. Thepilot symbols comprised in the respective preambles should bealternatively identical and orthogonal for the two transmittingantennas.

1. A transmitting device for transmitting data symbols and pilot symbolsin an OFDM transmission system having a plurality of transmissionantennas, the device comprising symbol generating means for generatingsaid data symbols and said pilot symbols, means for transmitting saiddata symbols and pilot symbols respectively by using a plurality ofsubcarriers of said OFDM transmission system via said plurality oftransmission antennas, wherein said symbol generating means generates afirst type pilot symbol and a second type pilot symbol having aninverted value of said first type pilot symbol so that a first pilotsymbol pattern in a frequency dimension contains at least said firsttype pilot symbol to be transmitted by using a predefined subcarrier andsecond type pilot symbol to be transmitted by using another predefinedsubcarrier, wherein said first pilot symbol pattern to be transmitted byusing one of said plurality of transmission antennas has a differentpattern from a second pilot symbol pattern to be transmitted by usinganother transmission antenna, and wherein at least some pairs of firstpilot symbols comprised in said first pilot symbol pattern and beingadjacent in a time dimension are respectively orthogonal to thecorresponding pairs of second pilot symbols comprised in said secondpilot pattern.
 2. A transmitting device for transmitting data symbolsand pilot symbols in an OFDM transmission system having a plurality oftransmission antennas, the device comprising symbol generating means forgenerating said data symbols and said pilot symbols, means fortransmitting said data symbols and pilot symbols respectively by using aplurality of subcarriers of said OFDM transmission system via saidplurality of transmission antennas, wherein said symbol generating meansgenerates a first type pilot symbol and a second type pilot symbolhaving an inverted value of said first type pilot symbol so that a firstpilot symbol pattern in a frequency dimension contains at least saidfirst type pilot symbol to be transmitted by using a predefinedsubcarrier and second type pilot symbol to be transmitted by usinganother predefined subcarrier, wherein said first pilot symbol patternto be transmitted by using one of said plurality of transmissionantennas has a different pattern from a second pilot symbol pattern tobe transmitted by using another transmission antenna, and wherein atleast some pairs of first pilot symbols comprised in said first pilotsymbol pattern and being adjacent in the frequency dimension arerespectively orthogonal to the corresponding pairs of second pilotsymbols comprised in said second pilot pattern.
 3. A transmitting devicefor transmitting data symbols and pilot symbols in an OFDM transmissionsystem having a plurality of transmission antennas, the devicecomprising symbol generating means for generating said data symbols andsaid pilot symbols, means for transmitting said data symbols and pilotsymbols by using a plurality of subcarriers of said OFDM transmissionsystem via said plurality of transmission antennas, wherein said symbolgenerating means generates a first type pilot symbol and a second typepilot symbol having an inverted value of said first type pilot symbol soas to create a first pilot symbol pattern in where said first and secondtype pilot symbols are allocated respectively in a frequency dimension,wherein said first pilot symbol pattern to be transmitted by using oneof said plurality of transmission antennas has a different pattern froma second pilot symbol pattern to be transmitted by using anothertransmission antenna, and wherein at least some pairs of first pilotsymbols comprised in said first pilot symbol pattern and being adjacentin a time dimension are respectively orthogonal to the correspondingpairs of second pilot symbols comprised in said second pilot pattern. 4.A transmitting device for transmitting data symbols and pilot symbols inan OFDM transmission system having a plurality of transmission antennas,the device comprising symbol generating means for generating said datasymbols and said pilot symbols, means for transmitting said data symbolsand pilot symbols by using a plurality of subcarriers of said OFDMtransmission system via said plurality of transmission antennas, whereinsaid symbol generating means generates a first type pilot symbol and asecond type pilot symbol having an inverted value of said first typepilot symbol so as to create a first pilot symbol pattern in where saidfirst and second type pilot symbols are allocated respectively in afrequency dimension, wherein said first pilot symbol pattern to betransmitted by using one of said plurality of transmission antennas hasa different pattern from a second pilot symbol pattern to be transmittedby using another transmission antenna, and wherein at least some pairsof first pilot symbols comprised in said first pilot symbol pattern andbeing adjacent in a time dimension are respectively orthogonal to thecorresponding pairs of second pilot symbols comprised in said secondpilot pattern.
 5. A transmitting device for transmitting data symbolsand pilot symbols in an OFDM transmission system, the device comprisingsymbol generating means for generating said data symbols and said pilotsymbols, means for transmitting said data symbols and pilot symbols byusing a plurality of subcarriers of said OFDM transmission system via aplurality of transmission antennas, wherein said symbol generating meansassigns either a first type pilot symbol or a second type pilot symbolhaving an inverted value of said first type pilot symbol to saidgenerated pilot symbols in a frequency dimension so that a first pilotsymbol pattern comprising said first and second type pilot symbols to betransmitted by using one of said plurality of transmission antennas hasa different pattern from a second pilot symbol pattern to be transmittedby using another transmission antenna, and wherein at least some pairsof first pilot symbols comprised in said first pilot symbol pattern andbeing adjacent in a time dimension are respectively orthogonal to thecorresponding pairs of second pilot symbols comprised in said secondpilot pattern.
 6. A transmitting device for transmitting data symbolsand pilot symbols in an OFDM transmission system, the device comprisingsymbol generating means for generating said data symbols and said pilotsymbols, means for transmitting said data symbols and pilot symbols byusing a plurality of subcarriers of said OFDM transmission system via aplurality of transmission antennas, wherein said symbol generating meansassigns either a first type pilot symbol to said generated pilot symbolsin a frequency dimension or a second type pilot symbol having aninverted value of said first type pilot symbol to said generated pilotsymbols in a frequency dimension so that a first pilot symbol patterncomprising said first and second type pilot symbols to be transmitted byusing one of said plurality of transmission antennas has a differentpattern from a second pilot symbol pattern to be transmitted by usinganother transmission antenna, and wherein at least some pairs of firstpilot symbols comprised in said first pilot symbol pattern and beingadjacent in the frequency dimension are respectively orthogonal to thecorresponding pairs of second pilot symbols comprised in said secondpilot pattern.
 7. A transmitting device for transmitting data symbolsand pilot symbols in an OFDM transmission system, the device comprisingsymbol generating means for generating said data symbols and said pilotsymbols, means for transmitting said data symbols and pilot symbols byusing a plurality of subcarriers of said OFDM transmission system via aplurality of transmission antennas, wherein said symbol generating meansis designed to create a first pilot symbol pattern in a frequencydimension comprising at least a first type pilot symbol and a secondtype pilot symbol having an inverted value of said first type pilotsymbol, wherein said first pilot symbol pattern assigned to one of saidplurality of transmission antennas has a different pattern from a secondpilot symbol pattern assigned to another transmission antenna, andwherein at least some pairs of first pilot symbols comprised in saidfirst pilot symbol pattern and being adjacent in a time dimension arerespectively orthogonal to the corresponding pairs of second pilotsymbols comprised in said second pilot pattern.
 8. A transmitting devicefor transmitting data symbols and pilot symbols in an OFDM transmissionsystem, the device comprising symbol generating means for generatingsaid data symbols and said pilot symbols, means for transmitting saiddata symbols and pilot symbols by using a plurality of subcarriers ofsaid OFDM transmission system via a plurality of transmission antennas,wherein said symbol generating means is designed to create a first pilotsymbol pattern in a frequency dimension comprising at least a first typepilot symbol and a second type pilot symbol having an inverted value ofsaid first type pilot symbol, wherein said first pilot symbol patternassigned to one of said plurality of transmission antennas has adifferent pattern from a second pilot symbol pattern assigned to anothertransmission antenna, and wherein at least some pairs of first pilotsymbols comprised in said first pilot symbol pattern and being adjacentin the frequency dimension are respectively orthogonal to thecorresponding pairs of second pilot symbols comprised in said secondpilot pattern.
 9. A transmitting device for transmitting data symbolsand pilot symbols in an OFDM transmission system having a plurality oftransmission antennas, the device comprising symbol generating means forgenerating said data symbols and said pilot symbols, means fortransmitting said data symbols and pilot symbols respectively by using aplurality of subcarriers of said OFDM transmission system via saidplurality of transmission antennas, wherein said symbol generating meansgenerates a first type pilot symbol and a second type pilot symbolhaving an inverted value of said first type pilot symbol so that a firstpilot symbol pattern in a time dimension comprises at least said firstand second type pilot symbols to be transmitted at different timepointsrespectively, wherein said first pilot symbol pattern to be transmittedby using one of said plurality of transmission antennas is differentfrom a second pilot symbol pattern to be transmitted by using anothertransmission antenna, and wherein at least some pairs of first pilotsymbols comprised in said first pilot symbol pattern and being adjacentin the time dimension are respectively orthogonal to the correspondingpairs of second pilot symbols comprised in said second pilot pattern.10. A transmitting device for transmitting data symbols and pilotsymbols in an OFDM transmission system having a plurality oftransmission antennas, the device comprising symbol generating means forgenerating said data symbols and said pilot symbols, means fortransmitting said data symbols and pilot symbols respectively by using aplurality of subcarriers of said OFDM transmission system via saidplurality of transmission antennas, wherein said symbol generating meansgenerates a first type pilot symbol and a second type pilot symbolhaving an inverted value of said first type pilot symbol so that a firstpilot symbol pattern in a time dimension comprises at least said firstand second type pilot symbols to be transmitted at different timepointsrespectively, wherein said first pilot symbol pattern to be transmittedby using one of said plurality of transmission antennas is differentfrom a second pilot symbol pattern to be transmitted by using anothertransmission antenna, and wherein at least some pairs of first pilotsymbols comprised in said first pilot symbol pattern and being adjacentin a frequency dimension are respectively orthogonal to thecorresponding pairs of second pilot symbols comprised in said secondpilot pattern.
 11. A transmitting device for transmitting data symbolsand pilot symbols in an OFDM transmission system having a plurality oftransmission antennas, the device comprising symbol generating means forgenerating said data symbols and said pilot symbols, means fortransmitting said data symbols and pilot symbols by using a plurality ofsubcarriers of said OFDM transmission system via said plurality oftransmission antennas, wherein said symbol generating means generates afirst type pilot symbol and a second type pilot symbol having aninverted value of said first type pilot symbol so as to create a firstpilot symbol pattern in where said first and second type pilot symbolsare regularly allocated in a time dimension, wherein said first pilotsymbol pattern to be transmitted by using one of said plurality oftransmission antennas is different from a second pilot symbol pattern tobe transmitted by using another transmission antenna, and wherein atleast some pairs of first pilot symbols comprised in said first pilotsymbol pattern and being adjacent in the time dimension are respectivelyorthogonal to the corresponding pairs of second pilot symbols comprisedin said second pilot pattern.
 12. A transmitting device for transmittingdata symbols and pilot symbols in an OFDM transmission system having aplurality of transmission antennas, the device comprising symbolgenerating means for generating said data symbols and said pilotsymbols, means for transmitting said data symbols and pilot symbols byusing a plurality of subcarriers of said OFDM transmission system viasaid plurality of transmission antennas, wherein said symbol generatingmeans generates a first type pilot symbol and a second type pilot symbolhaving an inverted value of said first type pilot symbol so as to createa first pilot symbol pattern in where said first and second type pilotsymbols are regularly allocated in a time dimension, wherein said firstpilot symbol pattern to be transmitted by using one of said plurality oftransmission antennas is different from a second pilot symbol pattern tobe transmitted by using another transmission antenna, and wherein atleast some pairs of first pilot symbols comprised in said first pilotsymbol pattern and being adjacent in a frequency dimension arerespectively orthogonal to the corresponding pairs of second pilotsymbols comprised in said second pilot pattern.
 13. A transmittingdevice for transmitting data symbols and pilot symbols in an OFDMtransmission system, the device comprising symbol generating means forgenerating said data symbols and said pilot symbols, means fortransmitting said data symbols and pilot symbols by using a plurality ofsubcarriers of said OFDM transmission system via a plurality oftransmission antennas, wherein said symbol generating means assignseither a first type pilot symbol or a second type pilot symbol having aninverted value of said first type pilot symbol to said generated pilotsymbols in a time dimension so that a first pilot symbol patterncomprising said first and second type pilot symbols to be transmitted byusing one of said plurality of transmission antennas is a differentpattern from a second pilot symbol pattern to be transmitted by usinganother transmission antenna, and wherein at least some pairs of firstpilot symbols comprised in said first pilot symbol pattern and beingadjacent in the time dimension are respectively orthogonal to thecorresponding pairs of second pilot symbols comprised in said secondpilot pattern.
 14. A transmitting device for transmitting data symbolsand pilot symbols in an OFDM transmission system, the device comprisingsymbol generating means for generating said data symbols and said pilotsymbols, means for transmitting said data symbols and pilot symbols byusing a plurality of subcarriers of said OFDM transmission system via aplurality of transmission antennas, wherein said symbol generating meansassigns either a first type pilot symbol or a second type pilot symbolhaving an inverted value of said first type pilot symbol to saidgenerated pilot symbols in a time dimension so that a first pilot symbolpattern comprising said first and second type pilot symbols to betransmitted by using one of said plurality of transmission antennas is adifferent pattern from a second pilot symbol pattern to be transmittedby using another transmission antenna, and wherein at least some pairsof first pilot symbols comprised in said first pilot symbol pattern andbeing adjacent in a frequency dimension are respectively orthogonal tothe corresponding pairs of second pilot symbols comprised in said secondpilot pattern.
 15. A transmitting device for transmitting data symbolsand pilot symbols in an OFDM transmission system, the device comprisingsymbol generating means for generating said data symbols and said pilotsymbols, means for transmitting said data symbols and pilot symbols byusing a plurality of subcarriers of said OFDM transmission system via aplurality of transmission antennas, wherein said symbol generating meansis designed to generate either a first type pilot symbol and a secondtype pilot symbol having an inverted value of said first type pilotsymbol in a time dimension as a type of said generated pilot symbols,wherein a first pilot symbol pattern, comprising said first and secondtype pilot symbols allocated in the time dimension, which is assigned toone of said plurality of transmission antennas is a different patternfrom a second pilot symbol pattern which is assigned to anothertransmission antenna, and wherein at least some pairs of first pilotsymbols comprised in said first pilot symbol pattern and being adjacentin the time dimension are respectively orthogonal to the correspondingpairs of second pilot symbols comprised in said second pilot pattern.16. A transmitting device for transmitting data symbols and pilotsymbols in an OFDM transmission system, the device comprising symbolgenerating means for generating said data symbols and said pilotsymbols, means for transmitting said data symbols and pilot symbols byusing a plurality of subcarriers of said OFDM transmission system via aplurality of transmission antennas, wherein said symbol generating meansis designed to generate either a first type pilot symbol and a secondtype pilot symbol having an inverted value of said first type pilotsymbol in a time dimension as a type of said generated pilot symbols,wherein a first pilot symbol pattern, comprising said first and secondtype pilot symbols allocated in the time dimension, which is assigned toone of said plurality of transmission antennas is a different patternfrom a second pilot symbol pattern which is assigned to anothertransmission antenna, and wherein at least some pairs of first pilotsymbols comprised in said first pilot symbol pattern and being adjacentin a frequency dimension are respectively orthogonal to thecorresponding pairs of second pilot symbols comprised in said secondpilot pattern.
 17. A transmitting device for transmitting data symbolsand pilot symbols in an OFDM transmission system having a plurality oftransmission antennas, the device comprising symbol generating means forgenerating said data symbols and said pilot symbols, means fortransmitting said data symbols and pilot symbols respectively by using aplurality of subcarriers of said OFDM transmission system via saidplurality of transmission antennas, wherein said symbol generating meansgenerates a first type pilot symbol and a second type pilot symbol beingorthogonal to said first type pilot symbol so that a first pilot symbolpattern in a frequency dimension contains at least said first type pilotsymbol to be transmitted by using a predefined subcarrier and secondtype pilot symbol to be transmitted by using other predefinedsubcarrier, wherein said first pilot symbol pattern to be transmitted byusing one of said plurality of transmission antennas has a differentpattern from a second pilot symbol pattern to be transmitted by usinganother transmission antenna, and wherein at least some pairs of firstpilot symbols comprised in said first pilot symbol pattern and beingadjacent in a time dimension are respectively orthogonal to thecorresponding pairs of second pilot symbols comprised in said secondpilot pattern.
 18. A transmitting device for transmitting data symbolsand pilot symbols in an OFDM transmission system having a plurality oftransmission antennas, the device comprising symbol generating means forgenerating said data symbols and said pilot symbols, means fortransmitting said data symbols and pilot symbols respectively by using aplurality of subcarriers of said OFDM transmission system via saidplurality of transmission antennas, wherein said symbol generating meansgenerates a first type pilot symbol and a second type pilot symbol beingorthogonal to said first type pilot symbol so that a first pilot symbolpattern in a frequency dimension contains at least said first type pilotsymbol to be transmitted by using a predefined subcarrier and secondtype pilot symbol to be transmitted by using other predefinedsubcarrier, wherein said first pilot symbol pattern to be transmitted byusing one of said plurality of transmission antennas has a differentpattern from a second pilot symbol pattern to be transmitted by usinganother transmission antenna, and wherein at least some pairs of firstpilot symbols comprised in said first pilot symbol pattern and beingadjacent in the frequency dimension are respectively orthogonal to thecorresponding pairs of second pilot symbols comprised in said secondpilot pattern.
 19. A transmitting device for transmitting data symbolsand pilot symbols in an OFDM transmission system having a plurality oftransmission antennas, the device comprising symbol generating means forgenerating said data symbols and said pilot symbols, means fortransmitting said data symbols and pilot symbols by using a plurality ofsubcarriers of said OFDM transmission system via said plurality oftransmission antennas, wherein said symbol generating means generates afirst type pilot symbol and a second type pilot symbol being orthogonalto said first type pilot symbol so as to create a first pilot symbolpattern in where said first and second type pilot symbols are allocatedrespectively in a frequency dimension, wherein said first pilot symbolpattern to be transmitted by using one of said plurality of transmissionantennas has a different pattern from a second pilot symbol pattern tobe transmitted by using another transmission antenna, and wherein atleast some pairs of first pilot symbols comprised in said first pilotsymbol pattern and being adjacent in a time dimension are respectivelyorthogonal to the corresponding pairs of second pilot symbols comprisedin said second pilot pattern.
 20. A transmitting device for transmittingdata symbols and pilot symbols in an OFDM transmission system having aplurality of transmission antennas, the device comprising symbolgenerating means for generating said data symbols and said pilotsymbols, means for transmitting said data symbols and pilot symbols byusing a plurality of subcarriers of said OFDM transmission system viasaid plurality of transmission antennas, wherein said symbol generatingmeans generates a first type pilot symbol and a second type pilot symbolbeing orthogonal to said first type pilot symbol so as to create a firstpilot symbol pattern in where said first and second type pilot symbolsare allocated respectively in a frequency dimension, wherein said firstpilot symbol pattern to be transmitted by using one of said plurality oftransmission antennas has a different pattern from a second pilot symbolpattern to be transmitted by using another transmission antenna, andwherein at least some pairs of first pilot symbols comprised in saidfirst pilot symbol pattern and being adjacent in the frequency dimensionare respectively orthogonal to the corresponding pairs of second pilotsymbols comprised in said second pilot pattern.
 21. A transmittingdevice for transmitting data symbols and pilot symbols in an OFDMtransmission system, the device comprising symbol generating means forgenerating said data symbols and said pilot symbols, means fortransmitting said data symbols and pilot symbols by using a plurality ofsubcarriers of said OFDM transmission system via a plurality oftransmission antennas, wherein said symbol generating means assignseither a first type pilot symbol to said generated pilot symbols in afrequency dimension or a second type pilot symbol being orthogonal tosaid first type pilot symbol to said generated pilot symbols in afrequency dimension so that a first pilot symbol pattern comprising saidfirst and second type pilot symbols to be transmitted by using one ofsaid plurality of transmission antennas has a different pattern from asecond pilot symbol pattern to be transmitted by using anothertransmission antenna, and wherein at least some pairs of first pilotsymbols comprised in said first pilot symbol pattern and being adjacentin a time dimension are respectively orthogonal to the correspondingpairs of second pilot symbols comprised in said second pilot pattern.22. A transmitting device for transmitting data symbols and pilotsymbols in an OFDM transmission system, the device comprising symbolgenerating means for generating said data symbols and said pilotsymbols, means for transmitting said data symbols and pilot symbols byusing a plurality of subcarriers of said OFDM transmission system via aplurality of transmission antennas, wherein said symbol generating meansassigns either a first type pilot symbol to said generated pilot symbolsin a frequency dimension or a second type pilot symbol being orthogonalto said first type pilot symbol to said generated pilot symbols in afrequency dimension so that a first pilot symbol pattern comprising saidfirst and second type pilot symbols to be transmitted by using one ofsaid plurality of transmission antennas has a different pattern from asecond pilot symbol pattern to be transmitted by using anothertransmission antenna, and wherein at least some pairs of first pilotsymbols comprised in said first pilot symbol pattern and being adjacentin the frequency dimension are respectively orthogonal to thecorresponding pairs of second pilot symbols comprised in said secondpilot pattern.
 23. A transmitting device for transmitting data symbolsand pilot symbols in an OFDM transmission system, the device comprisingsymbol generating means for generating said data symbols and said pilotsymbols, means for transmitting said data symbols and pilot symbols byusing a plurality of subcarriers of said OFDM transmission system via aplurality of transmission antennas, wherein said symbol generating meansis designed to create a first pilot symbol pattern in a frequencydimension comprising at least a first type pilot symbol and a secondtype pilot symbol being orthogonal to said first type pilot symbol,wherein said first pilot symbol pattern assigned to one of saidplurality of transmission antennas has a different pattern from a secondpilot symbol pattern assigned to another transmission antenna, andwherein at least some pairs of first pilot symbols comprised in saidfirst pilot symbol pattern and being adjacent in a time dimension arerespectively orthogonal to the corresponding pairs of second pilotsymbols comprised in said second pilot pattern.
 24. A transmittingdevice for transmitting data symbols and pilot symbols in an OFDMtransmission system, the device comprising symbol generating means forgenerating said data symbols and said pilot symbols, means fortransmitting said data symbols and pilot symbols by using a plurality ofsubcarriers of said OFDM transmission system via a plurality oftransmission antennas, wherein said symbol generating means is designedto create a first pilot symbol pattern in a frequency dimensioncomprising at least a first type pilot symbol and a second type pilotsymbol being orthogonal to said first type pilot symbol, wherein saidfirst pilot symbol pattern assigned to one of said plurality oftransmission antennas has a different pattern from a second pilot symbolpattern assigned to another transmission antenna, and wherein at leastsome pairs of first pilot symbols comprised in said first pilot symbolpattern and being adjacent in the frequency dimension are respectivelyorthogonal to the corresponding pairs of second pilot symbols comprisedin said second pilot pattern.
 25. A transmitting device for transmittingdata symbols and pilot symbols in an OFDM transmission system having aplurality of transmission antennas, the device comprising symbolgenerating means for generating said data symbols and said pilotsymbols, means for transmitting said data symbols and pilot symbolsrespectively by using a plurality of subcarriers of said OFDMtransmission system via said plurality of transmission antennas, whereinsaid symbol generating means generates a first type pilot symbol and asecond type pilot symbol being orthogonal to said first type pilotsymbol so that a first pilot symbol pattern in a time dimensioncomprises at least said first and second type pilot symbols to betransmitted at different timepoints respectively, wherein said firstpilot symbol pattern to be transmitted by using one of said plurality oftransmission antennas is different from a second pilot symbol pattern tobe transmitted by using another transmission antenna, and wherein atleast some pairs of first pilot symbols comprised in said first pilotsymbol pattern and being adjacent in the time dimension are respectivelyorthogonal to the corresponding pairs of second pilot symbols comprisedin said second pilot pattern.
 26. A transmitting device for transmittingdata symbols and pilot symbols in an OFDM transmission system having aplurality of transmission antennas, the device comprising symbolgenerating means for generating said data symbols and said pilotsymbols, means for transmitting said data symbols and pilot symbolsrespectively by using a plurality of subcarriers of said OFDMtransmission system via said plurality of transmission antennas, whereinsaid symbol generating means generates a first type pilot symbol and asecond type pilot symbol being orthogonal to said first type pilotsymbol so that a first pilot symbol pattern in a time dimensioncomprises at least said first and second type pilot symbols to betransmitted at different timepoints respectively, wherein said firstpilot symbol pattern to be transmitted by using one of said plurality oftransmission antennas is different from a second pilot symbol pattern tobe transmitted by using another transmission antenna, and wherein atleast some pairs of first pilot symbols comprised in said first pilotsymbol pattern and being adjacent in a frequency dimension arerespectively orthogonal to the corresponding pairs of second pilotsymbols comprised in said second pilot pattern.
 27. A transmittingdevice for transmitting data symbols and pilot symbols in an OFDMtransmission system having a plurality of transmission antennas, thedevice comprising symbol generating means for generating said datasymbols and said pilot symbols, means for transmitting said data symbolsand pilot symbols by using a plurality of subcarriers of said OFDMtransmission system via said plurality of transmission antennas, whereinsaid symbol generating means generates a first type pilot symbol and asecond type pilot symbol being orthogonal to said first type pilotsymbol so as to create a first pilot symbol pattern in where said firstand second type pilot symbols are regularly allocated in a timedimension, wherein said first pilot symbol pattern to be transmitted byusing one of said plurality of transmission antennas is different from asecond pilot symbol pattern to be transmitted by using anothertransmission antenna, and wherein at least some pairs of first pilotsymbols comprised in said first pilot symbol pattern and being adjacentin the time dimension are respectively orthogonal to the correspondingpairs of second pilot symbols comprised in said second pilot pattern.28. A transmitting device for transmitting data symbols and pilotsymbols in an OFDM transmission system having a plurality oftransmission antennas, the device comprising symbol generating means forgenerating said data symbols and said pilot symbols, means fortransmitting said data symbols and pilot symbols by using a plurality ofsubcarriers of said OFDM transmission system via said plurality oftransmission antennas, wherein said symbol generating means generates afirst type pilot symbol and a second type pilot symbol being orthogonalto said first type pilot symbol so as to create a first pilot symbolpattern in where said first and second type pilot symbols are regularlyallocated in a time dimension, wherein said first pilot symbol patternto be transmitted by using one of said plurality of transmissionantennas is different from a second pilot symbol pattern to betransmitted by using another transmission antenna, and wherein at leastsome pairs of first pilot symbols comprised in said first pilot symbolpattern and being adjacent in a frequency dimension are respectivelyorthogonal to the corresponding pairs of second pilot symbols comprisedin said second pilot pattern.
 29. A transmitting device for transmittingdata symbols and pilot symbols in an OFDM transmission system, thedevice comprising symbol generating means for generating said datasymbols and said pilot symbols, means for transmitting said data symbolsand pilot symbols by using a plurality of subcarriers of said OFDMtransmission system via a plurality of transmission antennas, whereinsaid symbol generating means assigns either a first type pilot symbol tosaid generated pilot symbols in a time dimension or a second type pilotsymbol being orthogonal to said first type pilot symbol to saidgenerated pilot symbols in a time dimension so that a first pilot symbolpattern comprising said first and second type pilot symbols to betransmitted by using one of said plurality of transmission antennas is adifferent pattern from a second pilot symbol pattern to be transmittedby using another transmission antenna, and wherein at least some pairsof first pilot symbols comprised in said first pilot symbol pattern andbeing adjacent in the time dimension are respectively orthogonal to thecorresponding pairs of second pilot symbols comprised in said secondpilot pattern.
 30. A transmitting device for transmitting data symbolsand pilot symbols in an OFDM transmission system, the device comprisingsymbol generating means for generating said data symbols and said pilotsymbols, means for transmitting said data symbols and pilot symbols byusing a plurality of subcarriers of said OFDM transmission system via aplurality of transmission antennas, wherein said symbol generating meansassigns either a first type pilot symbol to said generated pilot symbolsin a time dimension or a second type pilot symbol being orthogonal tosaid first type pilot symbol to said generated pilot symbols in a timedimension so that a first pilot symbol pattern comprising said first andsecond type pilot symbols to be transmitted by using one of saidplurality of transmission antennas is a different pattern from a secondpilot symbol pattern to be transmitted by using another transmissionantenna, and wherein at least some pairs of first pilot symbolscomprised in said first pilot symbol pattern and being adjacent in afrequency dimension are respectively orthogonal to the correspondingpairs of second pilot symbols comprised in said second pilot pattern.31. A transmitting device for transmitting data symbols and pilotsymbols in an OFDM transmission system, the device comprising symbolgenerating means for generating said data symbols and said pilotsymbols, means for transmitting said data symbols and pilot symbols byusing a plurality of subcarriers of said OFDM transmission system via aplurality of transmission antennas, wherein said symbol generating meansis designed to generate either a first type pilot symbol as a type ofsaid generated pilot symbols or a second type pilot symbol beingorthogonal to said first type pilot symbol in a time dimension as a typeof said generated pilot symbols, wherein a first pilot symbol pattern,comprising said first and second type pilot symbols allocated in thetime dimension, which is assigned to one of said plurality oftransmission antennas is a different pattern from a second pilot symbolpattern which is assigned to another transmission antenna, and whereinat least some pairs of first pilot symbols comprised in said first pilotsymbol pattern and being adjacent in the time dimension are respectivelyorthogonal to the corresponding pairs of second pilot symbols comprisedin said second pilot pattern.
 32. A transmitting device for transmittingdata symbols and pilot symbols in an OFDM transmission system, thedevice comprising symbol generating means for generating said datasymbols and said pilot symbols, means for transmitting said data symbolsand pilot symbols by using a plurality of subcarriers of said OFDMtransmission system via a plurality of transmission antennas, whereinsaid symbol generating means is designed to generate either a first typepilot symbol as a type of said generated pilot symbols or a second typepilot symbol being orthogonal to said first type pilot symbol in a timedimension as a type of said generated pilot symbols, wherein a firstpilot symbol pattern, comprising said first and second type pilotsymbols allocated in the time dimension, which is assigned to one ofsaid plurality of transmission antennas is a different pattern from asecond pilot symbol pattern which is assigned to another transmissionantenna, and wherein at least some pairs of first pilot symbolscomprised in said first pilot symbol pattern and being adjacent in afrequency dimension are respectively orthogonal to the correspondingpairs of second pilot symbols comprised in said second pilot pattern.